The present invention relates to an extruded aluminum manifold having three channels formed therein to facilitate operation of hydraulic switching valves for controlling intake and exhaust valves in a camless engine.
Internal combustion engines typically include intake and exhaust valves which are operated by cams on a camshaft associated with the engine. Camless engines with electrically or hydraulically controlled valves have been proposed to provide improved control of valve operation in order to achieve valve movement which does not depend upon the contours of a cam surface. For example, an electrically or hydraulically controlled engine may enable valves to open multiple times during an engine cycle, or not at all, such as in a cylinder deactivation system. Electrically or hydraulically controlled valves may make timing adjustment easier and provide fully flexible valve actuation control.
Various designs of hydraulic switching valves have been developed to enable potentially efficient implementation of hydraulic control for intake and exhaust valves on a camless engine.
The present invention provides an extruded aluminum manifold for a hydraulically actuated camless engine which enables implementation of the above mentioned hydraulic switching valves in a mass-produced camless engine.
More specifically, the invention provides a manifold for housing-high-pressure oil on a camless engine, including an extruded aluminum body having first and second ends, and having first, second and third extruded channels formed therein and each extending from the first end to the second end of the body. The body has a plurality of switching valve mounting bores configured to receive a plurality of switching valves operative to alternately communicate the channels with intake and exhaust valves of an engine to which the manifold is mounted.
Preferably, the body includes at least eight of the switching valve mounting bores formed therein. End caps are bolted to first and second ends of the body to enclose the first, second and third channels.
Extruding the aluminum body provides the high tensile and yield strength properties required to withstand the stresses induced by the high-pressure oil. Use of aluminum is preferred over other high strength materials such as steel because it weighs significantly less.
The extrusion allows the formation of long internal passages of uniform cross-section for containment of the oil. Long oil channels of substantial volume are preferred for valve control at the hydraulic switching valves to minimize pressure and noise pulses. One of the first, second and third channels is configured to receive high-pressure oil, and is substantially oval-shaped in vertical cross-section to provide reduced stress.
The hydraulic switching valve mounting bores or mounting pockets intersect or are connected with the appropriate channels to facilitate fluid communication.
The use of one oil manifold per row of engine valves, which is facilitated by use of an aluminum extrusion, minimizes sealing surfaces for reduced opportunity for leaks. Further, all potential leak paths at the hydraulic switching valve to manifold interface are internal to the manifold.
The invention also contemplates a method of manufacturing an oil manifold for a camless engine including the steps of: (A) extruding an aluminum member having first, second and third channels formed therein; (B) cutting the extruded aluminum member to a desired length to form a manifold body having first and second ends with the first, second and third channels extending from the first end to the second end; and (C) machining a plurality of switching valve mounting bores into the manifold body in fluid communication with the first, second and third channels.
The invention also provides a camless engine including a cylinder valve (i.e., an intake or exhaust valve) operatively associated with an engine cylinder and having a return spring biasing the cylinder valve toward a closed position. A fluid aperture is operatively associated with the valve to provide pressurized fluid to selectively counteract force of the return spring to actuate movement of the valve toward an open position. The fluid aperture is formed in an extruded aluminum manifold body having first, second and third channels formed therethrough for carrying oil at different pressures. A hydraulic switching valve is operatively positioned in the manifold body between the fluid aperture and at least two of the first, second and third channels to alternately communicate the two channels with the fluid aperture, wherein one of the two channels carries high-pressure oil and the other of the two channels carries low-pressure oil. Accordingly, high-pressure or low-pressure oil can communicate with the cylinder valve through the fluid aperture (via a force translator) to affect movement of the cylinder valve between the open and closed positions.